Proportion of days per month with precip > 0.2mm : ANUClimate 1.0, 0.01 degree, Australian Coverage

Proportion of days in each month with precipitation above 0.2 mm for the Australian continent between 1970-2014. The proportion of wet days per month is useful for estimating evaporation rates and water need and use, and also for estimating solar radiation. Modelled by using ANUSPLIN Version 4.5 to fit trivariate thin plate smoothing spline functions of longitude, latitude and vertically exaggerated elevation. Station elevations were 0.05 degree local averages of grid values from the GEODATA 9 second DEM version 3 as provided by ANUClimate_v1-0_digital-elevation-model-05deg-average_terrain_0-01deg. Anomaly based interpolation was not used because it gave no improvement over direct interpolation, due to the extensive daily precipitation network and the strong spatial coherence of daily rainfall occurrence. Monthly data values were obtained from Bureau of Meteorology daily rainfall data at stations where there were at least 25 days of record and no accumulated days of record, giving an average of 6320 data points per month between 1970 and 2014. Automated quality assessment rejected on average 35 data values per month (0.006%) with extreme studentised residuals. The root mean square of all individual cross validation residuals provided by the spline analysis is 0.060, corresponding to a root men square error in estimating the number of wet days of around 1.8 days per month. A comprehensive assessment of the analysis of the final interpolated grids is in preparation.